This invention relates to fabric and to pressure sensitive fabric tape.
Various woven fabrics are in use today as reinforcing material for adhesive-type or duct-type tapes. These fabrics are conventionally made of one hundred percent cotton, polyester/cotton blends or polyester/rayon blends in the machine direction (warp yarn) and one hundred percent cotton, polyester/cotton blends, polyester/rayon blends, or one hundred percent polyester in the cross-direction (weft yarn). The tape support fabric provides strength to the tape in processing and in use. It is desirable that such tape tear neatly when ripped by hand across the tape. Low count fabric has been used for tape support (having counts of from 44.times.28 to 18.times.9, for example).
FIG. 1 schematically shows a typical prior art tape 10 in exploded perspective view, having a woven tape support fabric 12 and a film backing layer 16. The woven tape support fabric 12 includes warp yarns 22 which run in the longitudinal or roll direction of the tape, interwoven with weft yarns 24 which run across (usually perpendicular to) the warp yarns. The backing layer 16 is typically laminated to the tape support fabric 12 by an adhesive layer 14. An adhesive layer 20 is applied, either as part of application of adhesive layer 14 or in a separate step, to the underside of tape support fabric 12. A conventional release coat 18 may also be applied to the backing to make it easier to separate the tape adhesive layer 20 from the backing 18 as the tape is peeled from the roll. Depending upon the material used for the tape support fabric 12, it may also be necessary to first apply an adhesion layer (not shown) to either side of the fabric to enable the adhesive layers 14, 20 to adhere to the fabric and to prevent delamination.
FIG. 2 is a cross-sectional view of tape support fabric 12 through line I--I of FIG. 1 looking along the warp direction of tape 10; the warp yarns 22 are shown intersecting a strand of weft yarn 24. The warp yarns typically have a sizing 26 applied longitudinally along the circumference of the yarn in a process known as "slashing". Coating the warp yarns with the sizing mixture provides both a protective capsule and also lubrication. The coating reduces the likelihood of breaking the yarns during the weaving process. As shown, the conventional tape support fabric 12 has a dimensional profile (or thickness) "A" defined by the peaks 28 of the weft yarn.
U.S. Pat. No. 4,303,724 discloses use of texturized weft yarns, such as polyester or nylon, in the filling of "30's" cotton warp gauze (24.times.20 or 20.times.12 count) to achieve better tear characteristics in adhesive tapes incorporating such fabrics. The patent also teaches that use of texturized weft yarns is beneficial because such yarns flatten out and spread more than non-texturized yarns. Thus, less adhesive mass is needed to unite the backing substrate (e.g., a pliable film), the texturized-weft fabric, and the mass into an integral tape.
U.S. Pat. No. 4,439,482 discloses a tape base fabric using a "flat" (i.e., untexturized) warp yarn of polyester fibers containing a specific heat-reactive chemical residue in the molecular chain of the yarn material. The yarn is heated to activate the residue and to modify the yarn when the yarn is used as the warp of the base fabric. The weft may also be a flat polyester yarn either with or without the polymer modification. The polymer modification changes the strength-elongation character of the yarn within the fabric.
In conventional yarn production, continuous filament yarns (such as polyester or nylon), as opposed to conventional blends and natural fibers, receive a very light coating of a mineral type oil to lubricate the yarn for subsequent high speed processes, such as beaming (i.e., winding the yarn onto wide aluminum spools or "section beams" for use in weaving). Normally the oil is applied at an add-on rate of three percent by yarn weight. Continuous filament yarns are readily available in untexturized and texturized form.